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Theoretical Study of the BF3-Promoted Rearrangement of Oxiranyl N-Methyliminodiacetic Acid Boronates.
Vallejos, Margarita M; Pellegrinet, Silvina C.
Afiliação
  • Vallejos MM; Laboratorio de Química Orgánica, IQUIBA-NEA, Universidad Nacional del Nordeste, CONICET, FACENA , Av. Libertad 5460, Corrientes 3400, Argentina.
  • Pellegrinet SC; Instituto de Química Rosario (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario , Suipacha 531, Rosario 2000, Argentina.
J Org Chem ; 82(11): 5917-5925, 2017 06 02.
Article em En | MEDLINE | ID: mdl-28493703
The mechanism of the rearrangement of oxiranyl N-methyliminodiacetyl (MIDA) boronates in dicholoromethane has been extensively investigated with density functional theory. Several reaction pathways were examined. Our results revealed that the most-favorable mechanisms for the BF3-promoted rearrangement of 2-phenyl oxiranyl MIDA boronate (1) and 1-phenyl oxiranyl MIDA boronate (24) comprise two steps: ring opening of the epoxide to a carbocation intermediate followed by migration of a MIDA-boryl group (for the reaction of 1) and hydrogen (for the reaction of 24), to give the same BF3-coordinated α-boryl aldehyde in both cases. The first step of the ring opening of the epoxide is the rate-determining step of these reactions. In the rearrangement step for the reaction of 1, the MIDA-boryl group migrates easily, probably because of its electron-rich sp3-hybridized boron center. For 24, the most-favorable pathway involves a rare boryl-substituted carbocation. The course of these reactions is mainly controlled by electronic effects, although steric effects are also significant. The higher energy barrier calculated for the unsubstituted oxiranyl MIDA boronate (31) explains the lack of reactivity in the studied BF3-promoted rearrangement.

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: J Org Chem Ano de publicação: 2017 Tipo de documento: Article País de afiliação: Argentina País de publicação: Estados Unidos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: J Org Chem Ano de publicação: 2017 Tipo de documento: Article País de afiliação: Argentina País de publicação: Estados Unidos